Insights to the enhanced photoelectrochemical sensing of Cr(VI) by piezoelectric effect based on ZnO/MoS2 heterojunction nanoarrays: Piezoelectric field-induced II-type to Z-scheme system

Numerous methods have been used to improve the photoelectrode materials to further enhance the performance of photoelectrochemical (PEC) sensors. However, the application of the piezoelectric effect in photoelectrochemical sensors has received less attention, and there is also little discussion on the relevant mechanisms. In this paper, a promising method is proposed for the first time to combine the piezoelectric effect with a photoelectrochemical sensor using ZnO/MoS2 nanoarrays as photoelectrodes. The results show that ZnO/MoS2 has better PEC performance and the highest photocurrent at a water flow speed of 950 rpm, 3.3 times higher than under non-stirring conditions. It can be related to the modulation of the energy band structure by the piezoelectric field, which transforms the II-type heterojunction into the Z-scheme heterojunction. With the piezoelectric effect, the enhanced photoelectrochemical sensor of Cr(VI) by piezoelectric effect has a wider detection range (0.008–640 µM) with a lower detection limit of 7 nM. Meanwhile, the detection limit is reduced by a factor of 7.7 compared to the absence of piezoelectric effects. This method of integrating the piezoelectric effect with PEC sensing provides a possible means of raising the detection efficiency of PEC sensors.